1. Field of the Invention
The present invention relates to a liquid ejection head that ejects a liquid, and a liquid ejection apparatus that has the liquid ejection head mounted thereon and performs recording onto a recording medium.
2. Description of the Related Art
A liquid ejection apparatus typified by an inkjet type liquid ejection apparatus has become widespread, because running cost at the time of recording is relatively inexpensive, and the operation sound is relatively quiet. One example of the liquid ejection head (hereinafter, also called a “recording head”) that is mounted on a liquid ejection apparatus is disclosed in Japanese Patent Application Laid-Open No. H10-6522.
The recording head disclosed in Japanese Patent Application Laid-Open No. H10-6522 includes a print head assembly having a nozzle, an electric wiring board such as an electric circuit, and a cartridge body. Note that the nozzle, the print head assembly and the cartridge body are also respectively called an ejection port, a recording element substrate and a support member.
The recording element substrate and the electric wiring board are electrically connected via a plurality of lead terminals. The support member has a recessed portion as a die cavity, and supports the recording element substrate by a bottom portion of the recessed portion. The lead terminal extends between the recording element substrate and a side surface of the recessed portion.
Further, the recording head includes a sealant formed from a thermosetting adhesive. The lead terminals are covered with the sealant, and the electrically connected portions between the lead terminals and the recording element substrate, and the electrically connected portions between the lead terminals and the electric wiring board are protected with use of the sealant.
As the manufacturing method of the recording head disclosed in Japanese Patent Application Laid-Open No. H10-6522, the following two methods are cited.
The first method is a method that fixes the recording element substrate and the electric wiring board to the support member, after connecting the recording element substrate and the electric wiring board via the lead terminals, and covering the lead terminals with the sealant. The second method is a method that covers the lead terminals with the sealant, after connecting the recording element substrate and the electric wiring board via the lead terminals and fixing the recording element substrate and the electric wiring board to the support member. The second method has the advantage that at the time of manufacturing the recording head, foreign matters hardly enter the nozzle plate in which the ejection port is formed.
The second method will be described in more detail. The sealant is applied onto the lead terminals after the recording element substrate and the electric wiring board are fixed to the support member, and the sealant flows into the gap between the recording element substrate and the side surface of the recessed portion from between the adjacent lead terminals. The gap is filled with the sealant, whereby the lead terminals are buried in the sealant. As a result, the lead terminals are covered with use of the sealant.
In the second method, in the case of the sealant being caused to flow into the aforementioned gap by one coating operation, the sealant traps air in the gap, and bubbles are sometimes formed in the gap. The bubbles rapidly expand at the time of curing by heating. By rapid expansion of bubbles, the sealant is scattered, and the lead terminals are not sealed by the sealant. As a result, imperfect sealing is likely to occur.
In the recording head disclosed in Japanese Patent Application Laid-Open No. H10-6522, an atmosphere communication passage that discharges gas is formed in the support member in order to restrain formation of bubbles and rapid expansion of the bubbles as above. One opening of the atmosphere communication passage is located in a side surface of the recessed portion, and the other opening of the atmosphere communication passage is located in an outer peripheral surface of the support member.
When the sealant is injected into the gap, the gas in the gap between the recording element substrate and the side surface of the recessed portion is discharged to the outside of the recording head through the atmosphere communication passage. Accordingly, the gas in the gap becomes difficult to trap by the sealant, and bubbles become difficult to form. Further, even if bubbles are formed, the gas in the bubbles is discharged to the outside through the atmosphere communication passage when the sealant is cured by heating. Therefore, the sealant is difficult to scatter, and imperfect sealing hardly occurs.
Incidentally, in a liquid ejection apparatus, a liquid (an ink) sometimes adheres to the ejection port by drying, and the recording head is brought into a state incapable of ejection. Therefore, a liquid ejection apparatus is proposed, which includes a cap and a suction pump for restraining adhesion of the ink in the ejection port, and returning the recording head that is in a state incapable of ejection into a state capable of ejection.
With the cap, at least the recording element substrate and the opening of the recessed portion are covered, and the recessed portion is hermetically sealed, when the recording head does not eject an ink. The recessed portion is hermetically sealed with use of the cap, whereby the ink hardly dries, and the ink hardly adheres to the ejection port.
The suction pump is connected to the cap. The suction pump operates and sucks the ink, in the state in which the opening of the recessed portion of the support member is covered with the cap. The ink is sucked to a cap side, whereby the ink adhering to the ejection port is removed, and the recording head returns to the state capable of ejection.
However, in the recording head disclosed in Japanese Patent Application Laid-Open No. H10-6522, adhesion of the ink cannot be sufficiently restrained, and the adhering ink cannot be sometimes removed with use of the suction pump, even if the opening of the recessed portion of the support member is covered with use of the cap. Hereinafter, the reason will be described specifically.
The coating amount of the sealant at the time of manufacturing the recording head sometimes varies, and when the coating amount of the sealant is not sufficient, one opening of the atmosphere communication passage is not covered with the sealant. Accordingly, even after the sealant is cured, the recessed portion still remains in communication with the outside of the recording head through the atmosphere communication passage. In the recording head disclosed in Japanese Patent Application Laid-Open No. H10-6522, the other opening of the atmosphere communication passage is located in the outer peripheral surface of the support member, and is not covered with the cap of the liquid ejection apparatus.
Since the other opening of the atmosphere communication passage is not closed, the recessed portion is not hermetically sealed even when the opening of the recessed portion is covered with the cap. As a result, the ink easily dries, and adherence of the ink cannot be sufficiently restrained. Further, even when the suction pump is operated, the gas outside the recording head is sucked through the atmosphere communication passage, and the adhering ink cannot be removed.